1. Field of the Invention
This invention relates generally to the removal of electronic components from a printed circuit board. More particularly, the invention relates to an apparatus and method for uniformly melting solder and removing a combination surface mount and plated through hole (PTH) device from a printed circuit board.
2. Description of the Related Art
Many electronic systems include a printed circuit board (PCB) with several surface mount and plated through hole (PTH) devices connected to the PCB. As used herein, the term surface mount and PTH device includes semiconductor packages, and connectors, such as matched impedance connectors. Frequently, surface mount and PTH devices are connected to the PCB by solder. Sometimes it is necessary to remove a surface mount or PTH device from a PCB. When removing a soldered device from a PCB, it is necessary to melt the solder that attaches the device to the PCB so that the device may be lifted from the PCB.
Removing a surface mount and PTH device from a PCB may cause problems. Problems may arise because flow control nozzles do not uniformly distribute a hot gas stream to the soldered connections holding a device onto a printed circuit board. A non-uniform hot gas stream may cause the solder connecting the device to the PCB to melt unevenly. When the device is lifted from the PCB, unevenly melted solder may cause greater resistance to removal at certain areas of the board. The greater resistance to removal may result in damage to the device and/or the PCB.
A surface mount and PTH device may be damaged upon prolonged exposure to heat. When removing a device, it is desirable to quickly and evenly heat and melt solder so that the device may be quickly and efficiently removed from a PCB. The device should not be exposed to heat for a prolonged period of time during the process of removing the device from the PCB.
A hot gas nozzle may be used to direct hot gas to solder that couples a device to a PCB. When the hot gas melts the solder, the nozzle is removed. Then, the device may be lifted from the PCB. A surface mount device may be lifted from the PCB with a vacuum cup. A surface mount and PTH device may necessitate the use of more force to remove the device from the PCB. A surface mount and PTH device may be lifted from the PCB with a pair of pliers. It is desirable to be able to heat and remove a device using only a single instrument, thus eliminating the need to use a vacuum cup or a pair of pliers to remove a device from a PCB.
When removing a device from a PCB, the device or the board may be damaged if the solder connection is not completely melted and force is applied to remove the device from the PCB. It is desirable to have an instrument that will remove the device from the board if the solder is completely melted, but will release the device if the solder is not completely melted.
The problems outlined above may in large part be solved by a nozzle that includes a grip mechanism. The nozzle may channel hot gas to melt solder that connects a device to a circuit board. The device may be a surface mount and plated through hole device. The grip mechanism of the nozzle may grasp the device so that the device can be removed from the circuit board by moving the circuit board away from the nozzle after the solder has been melted. Alternately, the device may be removed from the circuit board by moving the nozzle away from the circuit board. The grip mechanism within the nozzle may also provide proper hot gas flow distribution within the nozzle so that hot gas is delivered to an output end of the nozzle in a substantially uniform manner that facilitates uniform melting of solder holding the device to the circuit board.
The grip mechanism may include a spring mechanism. When the grip mechanism is used to remove the device from the circuit board, if the lifting force applied to the device exceeds a certain value, the spring mechanism will release the device. The release of the device may prevent damage to the device and damage to the circuit board when the solder connecting the device to the circuit board is not melted enough to allow the device to be removed from the circuit board.
An advantage of the nozzle is that the nozzle may have a size and shape that permits the reworking of the circuit board in confined areas. A further advantage of the nozzle is that the nozzle incorporates a grip mechanism. The grip mechanism increases the efficiency of removing a device by eliminating the use of pliers or other instruments during the removal of the device from the circuit board. After hot gas directed at solder connections by the nozzle melts the solder connecting the device to the circuit board, the grip mechanism may be used to securely grasp the device. Then, the nozzle may be raised from a position adjacent to the circuit board. Raising the nozzle will cause the device to be removed from the circuit board if the solder connections holding the device to the board were completely melted. If the solder connections were not completely melted, the gripping mechanism will release the device if the force applied to remove the device exceeds the force applied to the device by the gripping mechanism. Further advantages of the nozzle include having a device that is sturdy, durable, light weight, simple, efficient, reliable and inexpensive; yet the nozzle is easy to manufacture, install, maintain and use.